1. Field of the Invention
The present invention relates to a trimming circuit to be used for function setting or characteristics adjustment of a circuit in a semiconductor integrated circuit.
2. Description of the Related Art
In a circuit of a semiconductor device, such as a voltage detection circuit or a voltage setting circuit, a resistor circuit for setting a voltage is provided with a trimming circuit for resistors in order to adjust the voltage (see, for example, Japanese Patent Application Laid-open No. 2009-212415).
FIG. 5 is a circuit diagram of a conventional trimming circuit.
Description is given of the case of cutting a fuse F1 in a conventional trimming circuit 1.
A decode circuit 2 outputs a voltage of high level to a gate of an NMOS transistor N1, and outputs a voltage of low level to gates of NMOS transistors N2 to N4. The NMOS transistor N1 is turned ON and the NMOS transistors N2 to N4 are turned OFF. At this time, a current flows from a pad TRIM, which is a current supply terminal for fuse cutting, to a ground terminal via a diode D1, the fuse F1, and the NMOS transistor N1. The fuse F1 is cut by this current, and a resistor R1 is added in series into a resistor circuit. Further, a current also flows from the pad TRIM to the ground terminal via a diode D2, a fuse F2, a resistor R5, and the NMOS transistor N1. However, the current flows through the current limiting resistor R5, and hence the fuse F2 is not cut by this current.
In this way, a transistor to be turned ON is selected by the decode circuit 2 so that a desired fuse may be cut, thereby being capable of adding a desired resistor into the resistor circuit.
The conventional trimming circuit, however, needs a terminal (pad TRIM) to which a current for cutting a fuse is input. Therefore, there is a problem in that the chip size increases.